1 /* 2 * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the author nor the names of any co-contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * $FreeBSD: src/lib/libc/stdio/_flock_stub.c,v 1.16 2008/04/17 22:17:53 jhb Exp $ 30 */ 31 32 /* 33 * POSIX stdio FILE locking functions. These assume that the locking 34 * is only required at FILE structure level, not at file descriptor 35 * level too. 36 * 37 */ 38 39 #include "namespace.h" 40 #include <stdio.h> 41 #include <pthread.h> 42 #include "un-namespace.h" 43 44 #include "local.h" 45 46 void 47 _flockfile(FILE *fp) 48 { 49 pthread_t curthread = _pthread_self(); 50 51 if (fp->_fl_owner == curthread) 52 fp->_fl_count++; 53 else { 54 /* 55 * Make sure this mutex is treated as a private 56 * internal mutex: 57 */ 58 _pthread_mutex_lock(&fp->_fl_mutex); 59 fp->_fl_owner = curthread; 60 fp->_fl_count = 1; 61 } 62 } 63 64 /* 65 * This can be overriden by the threads library if it is linked in. 66 */ 67 void 68 _flockfile_debug_stub(FILE *fp, char *fname __unused, int lineno __unused) 69 { 70 _flockfile(fp); 71 } 72 73 int 74 _ftrylockfile(FILE *fp) 75 { 76 pthread_t curthread = _pthread_self(); 77 int ret = 0; 78 79 if (fp->_fl_owner == curthread) 80 fp->_fl_count++; 81 /* 82 * Make sure this mutex is treated as a private 83 * internal mutex: 84 */ 85 else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) { 86 fp->_fl_owner = curthread; 87 fp->_fl_count = 1; 88 } 89 else 90 ret = -1; 91 return (ret); 92 } 93 94 void 95 _funlockfile(FILE *fp) 96 { 97 pthread_t curthread = _pthread_self(); 98 99 /* 100 * Check if this file is owned by the current thread: 101 */ 102 if (fp->_fl_owner == curthread) { 103 /* 104 * Check if this thread has locked the FILE 105 * more than once: 106 */ 107 if (fp->_fl_count > 1) { 108 /* 109 * Decrement the count of the number of 110 * times the running thread has locked this 111 * file: 112 */ 113 fp->_fl_count--; 114 } else { 115 /* 116 * The running thread will release the 117 * lock now: 118 */ 119 fp->_fl_count = 0; 120 fp->_fl_owner = NULL; 121 _pthread_mutex_unlock(&fp->_fl_mutex); 122 } 123 } 124 } 125 126 /* 127 * Weak symbols for externally visible functions in this file: 128 */ 129 __weak_reference(_flockfile, flockfile); 130 __weak_reference(_flockfile_debug_stub, _flockfile_debug); 131 __weak_reference(_ftrylockfile, ftrylockfile); 132 __weak_reference(_funlockfile, funlockfile); 133